JP2009198771A - Focus detector and imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a focus detector and an imaging device appropriately detecting a focal point. <P>SOLUTION: This imaging device includes a micro lens array 161 including a plurality of micro lenses 161a two-dimensionally arranged therein, and a light receiver 162a for the micro lenses. The imaging device also include: a light receiving element 162 to receive the light flux from an imaging optical system through the micro lenses; a contrast detector 163 forming the image information based on the signals received on the light receiver to detect the contrasts in the directions X1-X3 in the image information; and a focus detector 163 selecting the direction to detect the focal point from the directions based on the contrasts and to detect the focusing state of the imaging optical system based on the received signals acquired on the light receiver of the micro lenses along the direction to detect the focal point. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a focus detection device and an imaging device.

The microlenses are arranged two-dimensionally, and a plurality of light receiving elements (photoelectric conversion elements) are provided for each microlens, and pass through different areas of the imaging optical system based on the light reception output obtained by the plurality of light receiving elements There is known an apparatus that detects a focus adjustment state of an imaging optical system by generating a pair of signal sequences corresponding to an image formed by a luminous flux and detecting a phase shift between the pair of signal sequences (Patent Document 1). .

JP 2007-11314 A

However, the conventional focus detection apparatus can generate a signal string pair in the direction along the arrangement direction of the microlenses, but has not been proposed for determining the signal string generation direction.

The problem to be solved by the present invention is to provide a focus detection apparatus and an imaging apparatus that can appropriately determine the generation direction of a signal sequence.

  The present invention solves the above problems by the following means. In addition, although the code | symbol corresponding to drawing which shows embodiment of this invention is attached | subjected and demonstrated, this code | symbol is only for making an understanding of invention easy, and is not the meaning which limits invention.

The focus detection apparatus and the imaging apparatus according to the invention include a microlens array (161) in which a plurality of microlenses (161a) are two-dimensionally arranged, and a light receiving unit (162a) provided corresponding to the microlens. , A light receiving element (162) that receives a light beam from the imaging optical system via the microlens, and image information is generated based on a light reception signal of the light receiving element, and a plurality of directions (X1 to X3) in the image information. A contrast detection means (163) for detecting the contrast of the light source, and a direction of focus detection from the plurality of directions based on the contrast, and a light receiving unit of the plurality of microlenses along the focus detection direction. Focus detection means (163) for detecting the focus adjustment state of the imaging optical system based on the received light signal. And butterflies.

In the above invention, the contrast detection means (163) can be configured to detect the contrast by convolving and integrating the image information. In this case, the contrast detection means (163) And can be configured to detect the contrast.

In the above invention, the light receiving element (162) includes a plurality of light receiving portions (162a) for each of the plurality of micro lenses (161a), and the contrast detecting means (163) is provided on the micro lens. The image information may be generated based on a light reception signal obtained by a part of the corresponding plurality of light receiving units. In this case, the contrast detection means (163) obtains the image information based on a signal obtained by integrating the light reception signals obtained by a part of the plurality of light receiving units (162a) over the plurality of microlenses (161a). Can be configured to generate.

In the above invention, the microlenses (161a) can be arranged in a honeycomb shape. In the above invention, the contrast detection means (163) can be configured to detect the contrast of the image information along the arrangement direction (X1 to X3) of the microlens (161a).

In the above invention, the contrast detection means (163) can be configured to detect the contrast with respect to the image information corresponding to a part of the plurality of microlenses (161a). In this case, a feature detection unit (163) that detects a feature portion of image information based on a light reception signal of the light receiving element (162) is provided, and the contrast detection unit (163) includes the plurality of microlenses (161a). The image information can be generated based on a light reception signal of the light receiving unit (162a) related to the microlens corresponding to the characteristic portion.

  According to the above invention, the generation direction of the signal sequence can be determined appropriately.

  In the following, an embodiment in which the above invention is applied to an interchangeable lens single-lens reflex digital camera will be described with reference to the drawings. However, the above invention is also applicable to any imaging device or lens fixed camera that adjusts the focus of a photographing lens. can do.

  FIG. 1 is a block diagram showing a single-lens reflex digital camera 1 (hereinafter simply referred to as a camera 1) according to an embodiment of the invention. The general configuration of the camera other than the configuration related to the focus detection device and the imaging device of the invention is described above. Some illustrations and explanations thereof are omitted.

  The camera 1 of this example includes a camera body 100 and a lens barrel 200, and the camera body 100 and the lens barrel 200 are detachably coupled by a mount unit 300.

The lens barrel 200 incorporates a photographing optical system including a photographing lens 210 including a focus lens 211 and a zoom lens 212, a diaphragm device 220, and the like.

The focus lens 211 is provided so as to be movable along the optical axis of the light beam L1 of the lens barrel 200, and its position is adjusted by the lens driving motor 230 while its position is detected by an encoder (not shown). The focus lens 211 can move in the direction of the optical axis L1 from the end on the camera body side (closest end) to the end on the subject side (infinite end) by the rotation of the rotating cylinder. Incidentally, the current position information of the focus lens 211 detected by the encoder is transmitted to the lens drive control unit 165 via the lens control unit 250, while the lens drive motor 230 is calculated based on this position information. The lens is driven by a drive signal received from the lens drive control unit 165 via the lens control unit 250 toward the in-focus position.

  The aperture device 220 is configured such that the aperture diameter around the optical axis L1 can be adjusted in order to limit the amount of light beam that passes through the imaging optical system and reaches the image sensor 110 and to adjust the blur amount. . The adjustment of the aperture diameter by the diaphragm device 220 is performed by transmitting an appropriate aperture diameter calculated in the automatic exposure mode from the camera control unit 170 via the lens control unit 250, for example. The aperture diameter is also adjusted by inputting the set aperture diameter from the camera control unit 170 to the lens control unit 250 by a manual operation by the operation unit 150 provided in the camera body 100. The aperture diameter of the aperture device 220 is detected by an aperture aperture sensor (not shown), and the current aperture diameter is recognized by the lens controller 250.

On the other hand, the camera body 100 includes a mirror system 120 for guiding the light beam L1 from the subject to the image sensor 110, the finder 135, the photometric sensor 137, and the focus detection optical system 161. This mirror system 120 has a quick turn mirror 121 that rotates about a rotation axis 123 by a predetermined angle between a subject observation position and a photographing position, and is supported by the quick turn mirror 121 to rotate the quick turn mirror 121. And a sub-mirror 122 that rotates together.

In FIG. 1, the state where the mirror system 120 is at the observation position of the subject is indicated by a solid line, and the state where the mirror system 120 is at the photographing position of the subject is indicated by a two-dot chain line. The mirror system 120 is inserted on the optical path of the light beam L1 in the state where the subject is in the observation position, while rotating to retract from the optical path of the light beam L1 in the state where the subject is in the photographing position.

The quick turn mirror 121 is formed of a half mirror, and in a state where the subject is at the observation position, a part of the light beam L2 from the subject is reflected by the quick turn mirror 121 and guided to the finder 135 side. The light beam L 4 is transmitted and guided to the sub mirror 122. Of the light beams reflected toward the viewfinder 135, the light beam L 3 scattered by the focusing screen 131 enters the photometric sensor 137. On the other hand, the sub mirror 122 is configured by a total reflection mirror, and guides the light beam L4 transmitted through the quick turn mirror 121 to the focus detection optical system 161.

Therefore, when the mirror system 120 is at the observation position, the light beam L1 from the subject is guided to the finder 135, the photometric sensor 135, and the focus detection optical module 161, and the subject is observed by the photographer, and exposure detection and focus adjustment are performed. State detection is performed. When the photographer fully presses the release button, the mirror system 120 rotates to the photographing position, the light beam L1 from the subject is guided to the image sensor 110, and the photographed image data is stored in a memory (not shown).

The image sensor 110 is fixed to a position on the camera body 100 on the optical axis of the light beam L1 from the subject and the planned focal plane of the photographing lens 210. The imaging element 110 is a two-dimensional array of a plurality of photoelectric conversion elements, and can be configured by a two-dimensional CCD image sensor, a MOS sensor, a CID, or the like.

The shutter 111 disposed on the front surface of the image sensor 110 is opened for the number of shutter seconds set based on the exposure calculation result or set by the photographer when the shutter button included in the operation unit 150 is fully pressed (during shutter release). Then, the image sensor 110 is exposed. The electrical image signal photoelectrically converted by the image sensor 110 is subjected to image processing by the camera control unit 170 and then stored in a memory (not shown). Note that the memory for storing the photographed image can be constituted by a built-in memory or a card-type memory.

On the other hand, part of the subject light reflected by the quick turn mirror 121 passes through a focusing screen 131 disposed on a surface optically equivalent to the image sensor 110 and is guided to the pentaprism 133, and is folded by the pentaprism 133. After being bent, it is guided to the photographer's eyeball through the eyepiece lens 134 along the optical axis L2. At this time, the transmissive liquid crystal display 132 superimposes and displays a focus detection area mark on the subject image on the focusing screen 131, and information relating to shooting such as a shutter speed, an aperture value, and the number of shots in an area outside the subject image. Is displayed. As a result, the subject, its background, photographing related information, and the like can be observed through the finder 134 in a state where the release is not performed.

The photometric sensor 137 is composed of a two-dimensional color CCD image sensor or the like, and divides the photographing screen into a plurality of regions and outputs a photometric signal corresponding to the luminance of each region in order to calculate an exposure value at the time of photographing. Image information detected by the photometric sensor 137 is output to the camera control unit 170 and used for automatic exposure control.

The operation unit 150 is a shutter release button or an input switch for the photographer to set various operation modes of the camera 1. Switching between the autofocus mode / manual focus mode and the autofocus mode also includes a one-shot mode / continuous mode. It is possible to switch between the numeric modes. Various modes set by the operation unit 150 are transmitted to the camera control unit 170, and the operation of the entire camera 1 is controlled by the camera control unit 170.

The camera body 100 is provided with a camera control unit 170. The camera control unit 170 includes peripheral components such as a microprocessor and a memory, and is electrically connected to the lens control unit 250 through an electric signal contact unit provided in the mount unit 300, and receives lens information from the lens control unit 250. At the same time, information such as the defocus amount and aperture diameter is transmitted to the lens controller 250. The camera control unit 170 reads out image information from the image sensor 110 as described above, performs predetermined information processing as necessary, and outputs the information to a memory (not shown). The camera control unit 170 controls the entire camera 1 such as correction of captured image information and detection of a focus adjustment state and an aperture adjustment state of the lens barrel 200.

  The focus detection optical system 161, the focus detection sensor 162, the focus detection calculation unit 163, and the lens drive amount calculation unit 164 constitute a phase difference detection type focus detection device that detects a defocus amount that represents the focus adjustment state of the photographing lens 210. To do.

  The focus detection apparatus of this example will be described with reference to FIGS.

  2 is a block diagram showing the configuration of the focus detection device, FIG. 3A is a diagram showing the optical arrangement of the focus detection device, FIG. 3B is a cross-sectional view showing the focus detection optical system 161 and the focus detection sensor 162, and FIG. FIG. 4B is an enlarged plan view showing one focus detection optical system 161 and the focus detection sensor 162. FIG. 4B is an enlarged plan view showing the arrangement state of the detection optical system 161 and the focus detection sensor 162. FIG. 2 is a block diagram showing the configuration of the focus detection calculation unit 163 shown in FIG. 1 in detail according to the processing procedure.

  The focus detection optical system 161 is a microlens array in which a plurality of microlenses 161a are two-dimensionally densely arranged (in a honeycomb shape) as shown in FIG. 4A, and the planned focus of the photographing lens 210 is shown in FIG. 3A. It arrange | positions in the vicinity of the position P1 used as a surface. Hereinafter, it is also referred to as a microlens array 161. The microlens array 161 can be arranged so as to coincide with the position P1 that becomes the planned focal plane, but can also be arranged shifted from the position P1 that becomes the planned focal plane. When they are arranged to coincide with each other, the portion becomes a dead zone when there is a contrast of the subject image between the microlenses 161a. However, such a dead zone can be avoided by shifting the portion.

The focus detection sensor 162 is a light receiving element array in which a plurality of photoelectric conversion elements 162a are densely arranged two-dimensionally as shown in FIG. 4A, and is arranged at a substantially focal position of the microlens array 161 as shown in FIG. 3B. ing. Hereinafter, it is also referred to as a light receiving element array 162. FIG. 3B shows the spread of the light beam received by the photoelectric conversion element 162a at or near the center of each microlens 161a.

  FIG. 4A is a plan view showing a part of the microlens array 161 and the light receiving element array 162, and is a view of the microlens array 161 viewed from the sub mirror 122 side. Although the photoelectric conversion element 162a is shown only behind a part of the microlenses 161a in the same figure, the photoelectric conversion element 162a is similarly arranged behind the other microlenses 161a.

  The microlens 161a of the present example has a shape obtained by cutting a circular microlens whose lens surface shape is indicated by a one-dot chain line into a regular hexagon, and has the same function as the circular microlens. The microlens array 161 has such regular hexagonal macro lenses 161a arranged in a honeycomb shape. By arranging regular hexagonal microlenses 161a in a honeycomb shape in this way, it is possible to avoid a dead zone in focus detection between lenses that occurs when circular microlenses are arranged. The vertical and horizontal directions in the figure coincide with the vertical and horizontal directions of the imaging screen imaged by the imaging element 110. Instead of arranging regular hexagonal microlenses 161a in a honeycomb shape, circular microlenses can be arranged in a square.

  On the other hand, the photoelectric conversion element array 62 disposed behind the microlens array 161 is a square array of square photoelectric conversion elements 162a. One photoelectric conversion element 162a is formed smaller than one microlens 161a, and as shown in an enlarged view in FIG. 4B, a plurality of photoelectric conversion elements 162a are included in a range in which one microlens 161a is vertically projected. Yes. These photoelectric conversion elements 162a are photoelectric conversion elements 162a provided corresponding to the microlenses 161a.

  Now, as described above, the microlens array 161 is disposed in the vicinity of the position P1 (a surface optically equivalent to the imaging surface of the imaging device 110) that is the planned focal plane of the imaging lens 210. The same optical image is projected. On the light receiving element array 162, the pupil image of the photographing lens 210 is formed by each micro lens 161a, and each photoelectric conversion element 162a of the light receiving element array 162 corresponds to each part of the pupil. If the conversion element 162a is selected and its output is synthesized, an image photographed with a diaphragm corresponding to the photoelectric conversion element 162a can be obtained.

The focus detection of this embodiment is performed according to the following procedure.

The A / D converter 163A of the focus detection calculation unit 163 shown in FIG. 2 converts the analog image signal output from the focus detection sensor (light receiving element array) 162 into a digital image signal and outputs it to the memory 163B. The memory 163B outputs this digital image signal in response to requests from the two-dimensional image generation unit 163C and the image signal extraction unit 163F.

When the focus detection area is selected, only the output from the photoelectric conversion element corresponding to the microlens corresponding to the predetermined range corresponding to the selected focus detection area is read out. FIG. 7 is a diagram showing a shooting screen 135A observed from the finder 135 including the focus detection area AFP. In this example, eleven focus detection areas AFP1 to AFP11 are set on the shooting screen 135A. This display is performed when the liquid crystal display 132 superimposes marks representing the positions of eleven focus detection areas on the subject image on the focusing screen 131. Then, the photographer operates the operation unit 150 to select a desired focus detection area AFP, or automatically selects the focus detection area AFP by a predetermined sequence based on data such as automatic exposure. For example, when the focus detection area AFP9 shown in FIG. 7 is selected, the output from the photoelectric conversion element corresponding to the microlens corresponding to a predetermined range centered on the focus detection area AFP9 is read.

The two-dimensional image generation unit 163C in FIG. 2 receives information on the focus detection area selected as the focus detection position from the camera control unit 170, extracts image data in a predetermined range centered on this position, and extracts the two-dimensional image. Generate.

At this time, the position of the photoelectric conversion element corresponding to the center of each microlens 161a is obtained from the position (image height) of the microlens with respect to the optical axis of the photographing optical system and the distance from the microlens to the pupil of the photographing lens 210. Image data of the photoelectric conversion element 162a corresponding to the center or the periphery of the microlens 161a is extracted from the image data stored in the memory 163B.

The two-dimensional image generated by the two-dimensional image generation unit 163 in this manner is an image photographed with a diaphragm corresponding to the photoelectric conversion element 162a. For example, when the size of the photoelectric conversion element 162a is 3 μm, the focal length of the microlens 161a is 200 μm, and the distance from the microlens array 161 to the pupil is 70 mm, the size of the photoelectric conversion element 162a on the pupil is 1 mm, A two-dimensional image substantially equal to an image obtained with a 1 mmφ aperture is generated. For example, if the focal length of the taking lens 210 is 50 mm, the F value is 50, and a pan-focus image with a deep focal depth is generated.

Here, as shown in FIG. 4A, the microlens array 161 of the present example has regular hexagonal microlenses 161a arranged in a honeycomb shape, and therefore the image data arrangement is also in a honeycomb shape. For this reason, when generating a two-dimensional image, it cannot be directly replaced with a square pixel array of equal intervals. That is, the center position of each microlens 161a in the microlens array 161 is such that even-numbered columns and odd-numbered columns are staggered and the horizontal interval is different from 2 / √3 when the vertical interval is 1. . For this reason, the two-dimensional image generation unit 163 of this example rearranges the image data based on such a honeycomb array in a square array at equal intervals by performing an interpolation operation or an extrapolation operation.

The feature detection unit 163D in FIG. 2 convolves the pan-focused two-dimensional image generated by the two-dimensional image generation unit 163 with respect to a plurality of directions, while convolving the other function f while translating one function f. Contrast is detected by performing a binomial operation in which the function g is added and added, and a detection direction with the largest contrast integrated value is selected.

The direction in which a dense image can be extracted in the microlens array 161 of the honeycomb-like array of this example is the horizontal direction X1 shown in FIG. 4A and the direction X2, which is ± 60 ° (± π / 3 rad) with respect to the X1 direction. Since there are three directions of X3, the contrast is detected by convolving and integrating the two-dimensional image in these three directions X1 to X3. However, contrast can be detected in directions other than these three directions X1 to X3.

The contrast detection in these three directions X1 to X3 can be detected by imaging an edge of an image having contrast in each direction by incorporating a differential filter into the convolution integral filter of the two-dimensional image. FIG. 5 is a determinant showing an example of the differential filter applied in this example. FIGS. 5A1 to 5A3 are determinants that represent Sobel filters (gradient filters) that are first-order differential filters of a two-dimensional image. The horizontal direction X1, the π / 3 direction X2, and the 2π / 3 direction X3, respectively. It is a filter which detects the edge part of contrast with respect to. On the other hand, FIGS. 5B1 to 5B3 are determinants showing a Laplacian filter which is a second-order differential filter of a two-dimensional image, and each of the horizontal direction X1, the π / 3 direction X2, and the 2π / 3 direction X3. It is a filter which detects the edge part of contrast with respect to.

In the contrast detection with respect to the three directions X1 to X3 in this example as shown in FIG. 4A, any differential filter can be used. The Sobel filter, which is the primary differential filter shown in FIGS. (A1) to (A3), is advantageous for detecting low-frequency images, and the Laplacian filter, which is the secondary differential filter, shown in FIGS. (B1) to (B3), Since it is advantageous for sharp detection, it can be applied as necessary.

In addition, since the primary differential filter shown to the same figure (A1)-(A3) is a determinant which goes to one direction of three directions X1-X3, the determinant which goes to the reverse direction of three directions X1-X3, In other words, as shown in (C1) to (C3) in the figure, it is possible to use a first-order differential filter in which the value of the determinant is reversed.

The result of performing edge detection of a two-dimensional image in such three directions X1 to X3 will be described with reference to a specific example. FIG. 6A is a diagram showing a two-dimensional image detected by the light receiving element array 162, and is an image in which the building B is reflected in the background of the person H wearing a shirt with a horizontal stripe pattern.

When this two-dimensional image is convolved and integrated using a differential filter in the horizontal direction X1 shown in FIG. 5 (A1), (B1), or (C1), an image as shown in FIG. 6B is obtained. In this image, although the vertical edges perpendicular to the horizontal direction X1, for example, the vertical pattern of the pillars and windows of the building B are sharply detected, the horizontal stripe pattern of the shirt worn by the person H is sharp. Not detected.

On the other hand, the two-dimensional image shown in FIG. 6 (A) is a π / 3 direction shown in any of FIGS. 5 (A2), (A3), (B1), (B2), (C2), and (C3). When convolution integration is performed using a differential filter with respect to X2 or 2π / 3 direction X3, an image shown in FIG. 6C is obtained. In this image, the horizontal stripe pattern of the shirt worn by the person H is sharply detected, and the pillars and windows of the building B in the background are not sharply detected.

As described above, the focus on the target subject may not be detected properly only by detecting the contrast in the horizontal direction X1, but the target subject's contrast is appropriately adjusted by detecting the contrast in a plurality of directions as in this example. Can be detected.

The feature detection unit 163D integrates the contrast obtained in each of the three directions X1 to X3. This integrated value is a value indicating the contrast amount for each direction in a predetermined area centered on the selected focus detection area AFP. Then, the integrated values in the three directions X1 to X3 are compared, and the directions X1 to X3 showing the largest contrast are determined. For example, in FIG. 4A, when the designated position of the focus detection area AFP is P1 and the contrast in the π / 3 direction X2 is the highest, the microlens 161a at the position P1 shown in FIG. A predetermined number of data is extracted. Hereinafter, the focus detection direction will be described as X2.

When the focus detection direction is determined to be X2, the feature detection unit 163D calculates the luminance difference, that is, the contrast of the photoelectric conversion elements 162a (elements constituting the two-dimensional image) of each microlens 161a in the determined focus detection direction X2. To do. When the luminance value of the two-dimensional image is V [i, j] (i is the row number of the photoelectric conversion element 162a in the X2 direction, and j is the column number of the photoelectric conversion element 162a in the X2 direction), the adjacent photoelectric conversion elements The contrast C [i, j] of 162a is
C [i, j] = | V [i, j] −V [i + 1, j] |
It can ask for.

  Then, the position of the photoelectric conversion element 162a at the center position of the microlens 161a having a relatively large calculated contrast C [i, j] is extracted as a feature point. Note that feature extraction is not limited to Equation 1 above, and any method that can detect a physical quantity related to contrast may be used.

  Returning to FIG. 2, the region setting unit 163E selects a feature point close to the center of the focus detection area AFP from the feature points extracted by the feature detection unit 163D, and sets a focus detection region around the selected feature point. . As shown in FIG. 4B, when the feature point extracted in the X2 direction is a position corresponding to the two microlenses 161X, the focus detection area AFA centering on the feature point is set as indicated by a two-dot chain line.

Even if the feature point exists at a position away from the center of the focus detection area AFP, the focus detection area AFA can be set around the feature point, and the focus detection area AFP selected in this way can be set. Regardless of the contrast, a high contrast portion can be set as the focus detection area AFA.

  The image signal extraction unit 163F in FIG. 2 reads out the output signals of the plurality of photoelectric conversion elements 162a corresponding to the microlenses 161a in the focus detection area AFA set by the area setting unit 163E from the memory 163B. A focus detection signal indicating an image shift amount due to a pair of light beams that have passed through different pupil regions, that is, a pair of focus detection signal sequences is generated.

Here, in order to perform the focus detection calculation, two signal sequences having a certain baseline length are required, and the direction of the signal sequence must substantially coincide with the direction of the baseline length. Therefore, two points selected in one microlens 161a are as shown in FIG. FIG. 8 shows an example of focus detection in the π / 3 direction X2, and positions P4 and P5 correspond to two virtual pupils that are paired with respect to the position P3 corresponding to the center of the microlens 161a. Is shown.

Here, if the distance from the center to the pupil when the base line is set in the horizontal direction X1 is 2 pixels, the coordinates of the position P3 with respect to (0, 0) when the π / 3 direction X2 shown in the figure is the base line. A pupil exists at the position (1, √3). Here, since the coordinate value of √3 is not an integer, the corresponding photoelectric conversion element 162a does not exist. However, it is substantially specified by weighted average of the outputs of the photoelectric conversion elements 162a around this position. The output at the selected position can be obtained.

The image signal extraction unit 163F extracts the first signal sequence {aj} and the second signal sequence {bj} (j is a natural number) and outputs the extracted signal sequence to the image shift amount calculation unit 163G.

The image shift amount calculation unit 163G calculates the defocus amount by executing the image shift calculation using the first signal sequence {aj} and the second signal sequence {bj}. In this calculation, first, a correlation calculation value Dk of a pair of images (signal sequences) is obtained from the first signal sequence {aj} and the second signal sequence {bj} by the following equation.

Dk = Σ | ai + k−bi |
Since Dk represented by Equation 2 is a discrete value, the minimum value can be regarded as the vicinity of the true minimum value. Therefore, the amount of deviation x is calculated by interpolating from the Dk values before and after the minimum value Dk. If the spatial change of the first signal sequence {aj} and the second signal sequence {bj} is expressed as a sine change, D (x) when a continuous function is used is the absolute value of the sine wave, and thus D (x ) Can be obtained by a simple linear approximation based on discrete Dk.

As shown in FIG. 9, let Dk be the minimum Dk, and Dk adjacent to this be Di + 1 and Di-1. The larger value is selected from Di + 1 and Di-1. In the example shown in the figure, Di-1 is larger, so Di-1 is selected. A straight line connecting the selected Di-1 and Di is defined as L1. Assuming that the slope of the straight line L1 is α, the straight line passing through Di + 1 with the slope of −α is L2. When the intersection point between the straight lines L1 and L2 is obtained, x at the intersection point is the above-described deviation amount x.

The lens drive amount calculation unit 164 in FIG. 2 calculates a lens drive amount Δd for making the shift amount x zero based on the shift amount x sent from the defocus calculation unit 163, and drives this lens. The data is output to the control unit 165.

The lens drive control unit 165 sends a drive command to the lens drive motor 230 while taking in the lens drive amount Δd sent from the lens drive amount calculation unit 164, and drives the focus lens 211 by the lens drive amount Δd.

As described above, in the camera 1 of this example, the contrast is detected in a plurality of directions such as the three directions X1 to X3, and the focus detection is performed in the direction with the largest contrast. Therefore, it is possible to appropriately detect the contrast of the target subject. it can.

  4A shows a light receiving element array 162 in which a total of 16 photoelectric conversion elements 162a of 4 vertical × 4 horizontal are arranged for each microlens 161a. However, the photoelectric conversion elements for each microlens 161a are shown in FIG. The number and arrangement of 162a are not limited to this. Further, instead of collectively arranging the photoelectric conversion elements 162a for each microlens 161a as shown in the figure, a light receiving element array for the plurality of microlenses 161a or the entire microlens array 161 as shown in FIG. 4B. 162 can also be arranged. Furthermore, instead of arranging the square photoelectric conversion elements 162a in a square shape, regular hexagonal photoelectric conversion elements can also be arranged in a honeycomb shape.

  In this example, the focus detection sensor 162 that is a two-dimensional sensor is provided separately from the image sensor 110. Instead, a micro lens 161a and a photoelectric conversion element 162a are provided in a part of the image sensor 110 with the same configuration. Thus, the focus can be detected by the above procedure.

It is a block diagram which shows the single-lens reflex digital camera which concerns on embodiment of invention. It is a block diagram which shows the structure of the focus detection apparatus of the camera shown in FIG. It is a figure which shows the optical arrangement | positioning of the focus detection apparatus of the camera shown in FIG. It is sectional drawing which shows the focus detection optical system and focus detection sensor of the camera shown in FIG. FIG. 2 is a plan view showing an arrangement state of focus detection optical systems and focus detection sensors of the camera shown in FIG. 1. It is a top view which expands and shows one focus detection optical system and focus detection sensor of the camera shown in FIG. It is a determinant which shows an example of the differential filter used with the focus detection apparatus of the camera shown in FIG. It is a figure which shows the two-dimensional image detected with the focus detection sensor of the camera shown in FIG. It is a figure which shows the result of having processed the image shown to FIG. 6A using the differential filter shown to FIG. 5 (A1), (B1), (C1). It is a figure which shows the result of having processed the image shown to FIG. 6A using any one of the differential filters shown to FIG. 5 (A2), (A3), (B1), (B2), (C2), (C3). . It is a figure which shows the imaging | photography screen observed with the finder of the camera shown in FIG. FIG. 2 is an enlarged plan view showing one focus detection optical system and a focus detection sensor for explaining a procedure when focus detection is performed in the π / 3 direction X2 in the camera focus detection apparatus shown in FIG. 1. 6 is a graph for explaining a method of calculating a shift amount x in the focus detection apparatus of the camera shown in FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Single-lens reflex digital camera 100 ... Camera body 110 ... Image pick-up element 161 ... Focus detection optical system (micro lens array)
161a ... Micro lens 162 ... Focus detection sensor (light receiving element array)
162a ... photoelectric conversion element 163 ... focus detection calculation unit 200 ... lens barrel 210 ... photographing lens

Claims (10)

A microlens array in which a plurality of microlenses are arranged two-dimensionally;
A light receiving element provided corresponding to the micro lens, and receiving a light beam from the imaging optical system through the micro lens;
Contrast detection means for generating image information based on a light reception signal of the light receiving element and detecting contrast in a plurality of directions in the image information;
A direction for focus detection is selected from the plurality of directions based on the contrast, and the imaging optical system is configured based on a light reception signal obtained by the light receiving unit of the plurality of microlenses along the focus detection direction. And a focus detection means for detecting a focus adjustment state. The focus detection apparatus according to claim 1,
The focus detection device, wherein the contrast detection means detects the contrast by convolving and integrating the image information. The focus detection apparatus according to claim 2,
The focus detection device, wherein the contrast detection means detects the contrast using a differential filter. In the focus detection apparatus according to any one of claims 1 to 3,
The light receiving element has a plurality of the light receiving portions for each of the plurality of microlenses,
The focus detection device, wherein the contrast detection unit generates the image information based on a light reception signal obtained by a part of the plurality of light receiving units corresponding to the microlens. The focus detection apparatus according to claim 4,
The focus detection device, wherein the contrast detection unit generates the image information based on a signal obtained by integrating light reception signals obtained by a part of the plurality of light receiving units over the plurality of microlenses. In the focus detection apparatus according to any one of claims 1 to 5,
The focus detection device, wherein the microlenses are arranged in a honeycomb shape. In the focus detection apparatus according to claim 4,
The focus detection device, wherein the contrast detection unit detects a contrast of the image information along an arrangement direction of the microlenses. In the focus detection apparatus according to any one of claims 1 to 7,
The focus detection apparatus, wherein the contrast detection unit detects the contrast with respect to the image information corresponding to a part of the plurality of microlenses. The focus detection apparatus according to claim 8, wherein
Comprising a feature detection means for detecting a feature portion of image information based on a light reception signal of the light receiving element;
The focus detection device, wherein the contrast detection unit generates the image information based on a light reception signal of the light receiving unit related to the microlens corresponding to the feature portion among the plurality of microlenses. An imaging apparatus comprising the focus detection apparatus according to claim 1.

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